Precision Organic Electrochemical Transistors for Single-Cell Electrophysiology

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Time-resolved in-situ metrology of organic electrochemical transistors to support the development of a dynamic device model Abstract Nontechnical: Organic electrochemical transistors (OECTs) are an emerging class of biocompatible organic semiconductor device that operate at very low voltages and with very high amplification. This combination of properties makes them attractive for external and implanted bioelectronics such as measuring electrical activity of muscles or neurons. However, progress is currently limited by incomplete understanding of the internal functioning of the transistors and also rudimentary fabrication methods that restrict integration and repeatability. The internal dynamics of the transistors will be studied with a number of microscopy techniques applied to operating transistors to inform the assembly of a theoretical device model. This model will guide the creation of new biomedical devices based on these transistors including the measurement of cellular action potentials. Technical: OECTs modulate the conductivity of a polymer semiconductor by injecting ions that replace dopant polyions, reversibly transforming the polymer channel into an insulator. This study will elucidate the spatio-temporal dynamics of lithographically-fabricated OECTs, based on the conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). The proposed techniques include real-time, electrochromic microscopy to elucidate the in situ doping dynamics during switching, scanning Kelvin probe microscopy to measure the spatial distribution of polymer doping on even finer scales, and AFM to reveal polymer morphology and swelling that are critical to understanding the physiological interface. These studies will elucidate the interplay of ion transport and doping, current flow, and mechanical properties in the active channel of working devices, leading to a better understanding of the structure-function relationship and validation of the first complete transient model of OECT function. This understanding will guide the study of improved fabrication methods including UV photolithography and surfactants that have been shown to improve performance and repeatability of other organic electronic devices. Repeatable photolithographic fabrication will enable device integration and precision measurements beyond current capability. Performance of these optimized sensors will be demonstrated by integration with nerve-like and skeletal myocyte cells, which will be bio-printed onto the gates of OECT arrays and a multi-electrode array for comparison. This will be performed with the assistance of a local bio-tech firm and two CU cell biology collaborators. A low-noise, multiplexed electrical interface to the OECT array will be designed and built as part of the undergraduate and outreach program.